A debate is heating up in Washington on whether the 40-year ban on U.S. crude exports should be lifted. Senator Lisa Murkowski (R - Alaska) is sponsoring a bill, which would allow U.S. companies to export oil. 'This is an opportunity for us to become an energy super power,' she told lawmakers in a Senate hearing on Tuesday. Murkowski, along with co-sponsor Senator John Hoven (R - North Dakota) said lifting the ban could also be good for consumers at the pump. 'More supply puts downward pressure on prices,' Hoven said. But some argue the bill could raise costs for refineries, which turn crude oil into gasoline. Refineries have access to U.S. oil, which is generally cheaper than oil overseas. That gives them a cost advantage to their international competitors. Shares of refineries Marathon Petroleum (MPC) and Valero Energy (VLO) posted modest gains on Tuesday. TheStreet's Scott Gamm reports from New York.